"O, they have lived long on the alms-basket of words.I marvel thy master hath not eaten thee for a word;for thou art not so long by the head as honorificabilitudinitatibus: thou art easierswallowed than a flap-dragon." - Costard, Love's Labour's Lost, Act V, Scene 1

HYPoThAlAmICoHYPoPHYSeAlS is the longest word that can be spelled using chemical symbols which refers to the pituitary and adjacent regions of the brain.

The longest word containing all six vowels, with each vowel occurring only once, is ANTISTREPHORRHYNCHUS (an extinct crustacean).
According to Philip Bennett, the longest words containing the six vowels in alphabetical order are PANCREATICODUODENOSTOMY (surgical formation of an artificial opening connecting the pancreas to the duodenum) and PANCREATICODUODENECTOMY (the most commonly used operation for attempting to remove a cancer of the exocrine pancreas completely) . PNEUMONOULTRAMICROSCOPICSILICOVOLCANOCONIOSIS (45 letters; a lung disease caused by breathing in certain particles) is the longest word in any English-language dictionary. (It is also spelled -koniosis.) is an alleged lung disease caused by the inhalation of very fine silica dust found in volcanoes.